There is provided a method for preparing an alumina bound, zeolite catalyst, wherein a zeolite of low silanol content is used as the source of zeolite used to prepare the catalyst. This catalyst may be combined with at least one hydrogenation component and used to hydrocrack hydrocarbons, such as gas oils.
Hydrocracking is a versatile petroleum refining process which enjoys widespread use in the refining industry. Hydrocracking has the ability to process a wide range of difficult feedstocks into a variety of desirable products. Feedstocks which may be treated by this process include heavy naphthas, kerosenes, refractory catalytically cracked cycle stocks and high boiling virgin and coker gas oils. At high severities, hydrocracking can convert these materials to gasoline and lower boiling paraffins; lesser severities permit the higher boiling feedstocks to be converted into lighter distillates such as diesel fuels and aviation kerosenes.
Hydrocracking is conventionally carried out at moderate temperatures of 350.degree. C. to 450.degree. C. (650.degree. F. to 850.degree. F.), because the thermodynamics of the hydrocracking process become unfavorable at higher temperatures. In addition, high hydrogen pressures, usually at least 5600 kPa (800 psig) are required to prevent catalyst aging and so to maintain sufficient activity to enable the process to be operated with a fixed bed of catalyst for periods of one to two years without the need for regeneration.
The catalysts used for hydrocracking usually comprise a transition metal such as nickel, cobalt, tungsten or molybdenum on an acidic support such as alumina or silica-alumina although noble metals such as platinum may also be used. Combinations of metals such as nickel with tungsten have been found to be extremely effective with a wide variety of feedstocks as has the presulfiding technique which is now widely employed.
Hydrocracking processes using the hydrogen form of zeolite Y as the acidic component are described, for example, in U.S. Pat. Nos. 3,269,934 and 3,524,809, and in "Preparation of Catalysts III", ed. by G. Poncelet, P. Grange, and P. A. Jacobs, Elsevier Science Publishers, 587 (1983).